The long-term objectives of this project are to assess germline and somatic mutation rates, and individual fitness in a natural population of mammals exposed to complex mixtures of environmental toxins. This project is the first in a series to evaluate the use of DNA fingerprinting as a diagnostic molecular tool to detect significant exposure of wild mammals to environmental mutagens. Availability of such a diagnostic tool is absolutely essential to identify mutagenicity, and ultimately increased risk of cancer for rapidly accumulating environmental chemicals. Specifically, germ line mutation rates will be estimated by determining novel minisatellite fragments in deer mouse progeny for mouse colonies derived from one contaminated and one uncontaminated site. DNA will be extracted from peripheral blood leukocytes obtained from parents and offspring, and several multilocus, minisatellite probes (i.e., Jeffreys' 33.6, and 33.15, synthetic M-probe) will be used to generate independent, highly variable RFLP patterns (Objective A). Levels of exposure to heavy metals will be estimated through soil and tissue samples derived from the contaminated site, and the uncontaminated control site. Multilocus DNA fingerprinting will be used to assess somatic mutation rates at hypervariable minisatellite loci for any detected tumors among adult deer mice (Objective B). Fitness consequences of exposure to pollutants will be assessed based on asymmetry of morphological traits and reproductive performance. In order to estimate morphological asymmetry, bilateral morphological measurements will be taken for all individuals. Reproductive performance of all breeding pairs will be monitored by recording number of pups per breeding pair (litter size), survival of pups to weaning (viability), and mass of pups at birth and weaning. (Lacy and Ballou 1998) (Objective C). To distinguish potential fitness reduction due to acute toxicity versus germline mutations, breeding colonies derived from the laboratory-raised F1 generation will be established, and their reproductive success and offspring survival will be monitored (Objective D)